1. Field of the Invention
This invention relates to the mechanical arts. In particular, it relates to a method for manufacturing a composite pad and more particularly to a method for manufacturing a composite pad to be worn as part of an orthopedic brace and the pads produced by the method.
2. Discussion of the Related Art
Composite pads are used in great variety of environments. One particularly demanding environment is found where a composite pad is used to cushion an orthopedic brace.
Orthopedic braces are commonly worn to stabilize a skeletal joint that has been weakened by injury or other infirmity. The brace is typically made of a number of rigid structural components dynamically linked by hinges to support the joint when the wearer is active. The brace is positioned such that the hinges traverse the joint being stabilized, while the rigid components are secured to the body above and below the joint.
Pads are often used to cushion the contact between the body and the rigid components of the brace, because the pads conform to the body of the user and provide a soft barrier between the brace and the body. Typically, such pads are made of porous, resilient foams, such as a polyvinyl acetate or polyurethane foams. However, it has proven impractical and undesirable to make a pad consisting only of a porous foam. This is because the foam is readily degraded and can be abrasive when placed in direct contact with the wearer. Consequently, in the design of pads for orthopedic braces, it is a desideratum to include a layer of a durable, but soft, material compatible with the wearer to serve as an interface between the wearer and the foam. Further, as mentioned above, the pads are used in an environment where there is considerable movement. Not only does this contribute to the deterioration of the pad, but it has proven difficult to secure a foam directly to the brace in order to prevent the pad from being displaced. Consequently, it is also a desideratum to provide a backing to the pad that is both durable and specifically adapted to be secured to the brace.
It has also proved difficult to design a fully satisfactory and optimum pad having a foam material sandwiched between two outer layers. In order to ensure the structural integrity of such a pad, it is generally necessary to weld or otherwise seam the two layers along the perimeter of the pad. In the prior art, pads have been sealed or welded utilizing a die tool that produces a wide seal or weld. One reason for the wide seal or weld is to ensure that the pad may subsequently be cut or severed from the excess material along the resulting seam without compromising the effectiveness of the seal. Conventionally, this sharp or severing action has been accomplished by use of a separate tool. As a result, substantial tolerances must be provided to account for film stretching, variations in machine operation, and registration between the sharp tool and the seal. Unfortunately, the resulting seam not only tends to be unsightly, but can cause discomfort as it chafes against the wearer.
Other prior art pads have a seam formed by sewing a bias tape that is folded over the edges of the outer layers. Pads of this construction can be less durable, less attractive to the eye and require more manufacturing time. In addition the bias tape can irritate the wearer.
Accordingly, there has existed a need for a simple and effective method for manufacturing a composite pad that provides significant cushioning and is durable, but has a layer providing a smooth, pliable surface for contacting the wearer, and is effectively sealed along the perimeter of the pad to a second layer for securing the pad to the brace. There has existed a further need for a method for sealing the two layers in such a manner that the resulting seam is not unsightly and does not irritate the wearer. There has existed a still further need for the pads formed by such methods. The present invention satisfies these and other needs and provides further related advantages.